The Clinical Consortium Core of this Program provides an integrated infrastructure with which to develop, evaluate, and recommend clinical trials for patients with CLL. In addition, the Clinical Consortium will identify the clinical significance of established and proposed therapeutic endpoints, test promising new agents, and define clinical parameters that correlate with disease activity and prognosis. To these ends we have the following specific aims: 1. Provide clinically relevant information to the multi-institutional database of this proposal. 2. Use the database to further understanding of CLL by correlating clinical and biologic data. 3. Develop predictive models for probability of response and survival and treatment at different phases of CLL. These models will be in an ongoing fashion evaluate the efficacy of therapy. 4. Explore the association of cytogenetic, molecular genetic, and immunologic changes with phases in the development of CLL. 5. Study new agents that address exploitable mechanisms in CLL as they become available, e.g. Flavopiridal and clofarabine. Clinical trials will be tightly coupled with pharmacology and biologic data to develop the most rational design. 6. Evaluate the efficacy, safety, and relevance of gene therapy in CLL. 7. Explore promising new agents such as Compound 506U78 and the monoclonal antibodies CAMPATH-1H and IDEC C2B8 in Phase II studies. Identify agents which should proceed to rational mechanism- based Phase II combination studies and Phase III clinical trials. 8. Develop and Advisory Committee (the CRC Clinical Trials Group) to review proposed clinical Phase I/II trials and make recommendations to established Cooperative Groups regarding Phase III clinical trials. 9. Develop testable clinical strategies to achieve molecular complete remissions in CLL. These strategies will incorporate chemotherapeutic, monoclonal antibody, transplantation, and vaccine approaches when available.